We undertook a study amongst adolescents from Mabile High School in Bamako, Mali. The goal of the study was to determine the knowledge, attitudes and practices of high school students around STI/AIDS and family planning. It was a transversal study using a stratified sampling method. A total of 322 students between ten and 19 years of age were included in the study (191 boys, 131 girls) This study demonstrates that high school students do not often family planning services (only 13.4% of those who knew of the existence of such used them). The method of contraception most often used is still the condom (92.5%). HIV is the most well know STI (97.5%) followed by gonorrhea (45%). An absence of communication between adolescents and their parents around family planning and STI/AIDS was apparent in that information was most often received on these topics through the media (96.3% for family planning, 97.5% for AIDS) followed by friends (72.4% for family planning and 81.7% for AIDS). 59.3% of the students are sexually active. Of sexually active students, 41.3% have had sexual relations with a casual partner and 75.9% with at last two partners. Given their high number of partners and a lack of systematic condom usage, it is apparent that sexually active high school students practice high risk sexual behaviors. It is therefore crucial to develop methods to lead to an improvement in behaviors amongst adolescents.